The present invention relates to a method and related systems for navigation in an enclosed area. More particularly, the invention relates to method and apparatus which can be used to cause an automated device to move and to perform predetermined tasks within an enclosed area.
The use of automated devices is widespread nowadays, and finds countless applications. For instance, robots perform very precise and delicate tasks in the construction of electronic devices, or in medicine and aviation. Robots are also used in uses which require motion, notably, for automatic warehouses, where goods are retrieved and stored by means of computer-actuated robots. Other applications include, e.g., fetching raw materials in the course of industrial manufacturing, and removing and packaging finished pieces. In everyday""s life, attempts have also been made to exploit robots for lawn mowing and for vacuum cleaning.
The major drawback of mobile robots, which the art has so far been unable to overcome, is the fact that their movements are limited to well predefined paths, normally requiring that they move along rails, or that they be provided with expensive navigation signs, positioned within the area in which they move, which operate as xe2x80x9cstationsxe2x80x9d which redefine the exact position of the robot, and from which the program may direct the robot to the next station. These intermediate signs are expensive, take up space, and are inconvenient to use, since they must be very precisely positioned and cannot be easily moved.
Another approach involves providing an area delimited by boundaries recognizable by the robot, and permitting the robot to effect a random walk therein, during which random walk it carries out its tasks. This approach entails severe drawbacks: first of all, when the robot moves within a predefined area by random walk, there is no way to ensure that the whole area will be covered by the tool which must operate thereon. As a result, even though the robot may operate for a long period of time, unworked areas may be left at the end of the operation. Secondly, if the area to be worked is irregular, or if it presents xe2x80x9cislandsxe2x80x9d, viz. areas which must not be worked, the random walk may lead to imperfect operation around such islands, as well as at those locations where the perimeter is of irregular shape. Thirdly, because the operation of the robot is not programmed to obtain a predetermined coverage, it is necessary to allow the random walk to go on for a long period of time, so as to increase the chances of covering a major portion of the area to be worked. This is not only energy consuming, but also leads to an increased wear of the equipment, and may also be environmentally undesirable due, e.g., to noise or other pollution caused by the operation of the robot. Even if the robot is operated by sun energy, most of the aforesaid problems are not overcome, and additional problems exists, connected with such a mode of operation. For instance, the robot may not work properly in areas of the world where sun radiation is scarce or low, and may be inoperative for substantial parts of the day, e.g., on cloudy weather.
A further approach involves preprogramming the robot with a blueprint of its designated area of operation, such as a floor map of a building in which a robot is to operate. This approach has two major drawbacks:
a) it requires preprogramming by the user, which makes in unpractical for extensive consumer use; and
b) it requires that such preprogramming is repeated each time something changes in the work area.
It is therefore clear that it would be highly desirable to be able to provide means by which automated mechanisms may move and perform their task within a predetermined area, without being hindered by the need for predefined paths and rails, or by intermediate navigation signs or preprogramming, and which may carry out their task in a predetermined manner, without relying on random occurrences and/or on unstable energy sources.
It has now been found, and this is an object of the present invention, that it is possible to free automated mechanisms operating within an enclosed zone from the need for preprogramming or predefined paths and rails, and from the need for intermediate navigation aids, and this to overcome the drawbacks of the prior art and to provide means by which a robot may perform its tasks within an enclosed area in a manner free from such limitations, with high precision and in a minimal period of time.
It is an object of the present invention to provide a navigation method which fulfills the aforementioned goals.
It is another object of the invention to provide means which can be used in systems utilizing the method of the invention.
Other objects of the invention will become apparent as the description proceeds.
The method for automatically operating a robot within an enclosed area, according to the invention, comprises the steps of:
providing a boundary along the perimeter of the working area, the said boundary being detectable by a proximity sensor;
providing boundaries along the perimeter of each area enclosed in the working area, in which it is desired that the robot should not operate, the said boundaries also being detectable by a proximity sensor;
providing a proximity sensor positioned on the robot;
providing processing means connected to the said proximity sensor and receiving an input therefrom;
providing location means on the said robot, to determine the coordinates of the robot relative to an arbitrary origin, at any specific time;
providing direction finding means;
providing memory means to store values generated by the said processing means and, optionally, by the said location means;
causing the robot to move along each of the boundaries provided around or within the said working area, to detect the said boundaries and to memorize their shape, and to store in the memory means values representative of the coordinates of the said boundaries, relative to an arbitrary origin, thereby to generate a basic map of the working area;
when the robot is to operate within the said area:
(a) causing the robot to start from a starting point having known coordinates within the basic map of the working area;
(b) continuously determining the coordinates of the robot by analyzing data obtained from the location means and by detecting the vicinity of a boundary; and
(c) correcting the actual position of the robot on the basic map by comparing the calculated and the actual coordinates of each detected boundary.
By xe2x80x9crobotxe2x80x9d it is meant to indicate any autonomously operating device, which may carry out pre-programmed tasks with one or more tools, while moving in the process from one location to another.
According to a preferred embodiment of the invention, the location means comprise movement measuring means, such as an odometer or the like device, to measure the distance traveled by the robot, e.g., by measuring the number of revolutions of a wheel. As stated, direction finding means are also provided, so as to provide information on the direction in which the robot travels at any given time, which is needed in order to determine the coordinates of the robot on the map. The direction finding means can be of any suitable type, e.g., may comprise a compass.
While, as stated, it is an object of the invention to utilize relatively inexpensive devices for the operation of the robot, it is of course possible to employ more expensive and sophisticated equipment, without exceeding the scope of the invention. Thus, for instance, it is possible to employ range-finding means, such as a laser range-finder or RF range finders, to determine the distance of the robot from one or more given locations, at any given time, instead of, or in addition to, using an odometer or the like device to measure the distance traveled. However, any such modifications will be apparent to the skilled person, and therefore are not discussed herein in detail.
According to a preferred embodiment of the invention, the boundary which is detectable by a proximity sensor comprises a metallic wire through which electric current flows, and the proximity sensor comprises a magnetic field detector. According to another preferred embodiment of the invention, the boundary which is detectable by a proximity sensor comprises passive metallic means which is excitable by a magnetic field, and the proximity sensor comprises an electric field detector. In still another preferred embodiment of the invention the boundary which is detectable by a proximity sensor comprises passive magnetic means, and the proximity sensor comprises a magnetic field detector. Of course, the boundary may be marked by continuous or by discontinuous marking means, or by combinations thereof.
In still another alternative embodiment of the invention, the boundary which is detectable by a proximity sensor comprises a guide wire through which an acoustic signal passes, and the proximity sensor comprises an acoustic detector.
A further improvement in the precision of the determination of the actual coordinates of the robot on the map, at any given time, can be obtained by further providing on the boundaries a plurality of individually recognizable markers. Thus, when the robot reaches the boundaries, it not only identifies them by the proximity sensor, but may also receive the exact coordinates on the boundaries assigned to the specific marker it has detected. According to a preferred embodiment of the invention, when provided, the markers are substantially located at even distances from one another. Suitable markers will be easily recognized by the skilled person, and may comprise, e.g., an RF tag or magnetic tag.
As stated, according to another preferred embodiment of the invention, the distance-measuring means comprise an odometer or the like device, coupled to the wheels of the robot.
As stated, the robot, when initialized, moves along the boundaries and memorizes their shape. Such memorization may be carried out in a number of ways. For instance, the shape can be memorized by taking continuous or discontinuous readings of the compass and the odometer, and any such readings are then continuously integrated, to give the full coordinates of the boundaries.
The method of the invention can be exploited in a variety of uses, and is not limited to any particular field of application. One particularly interesting use, however, to which reference will be made also hereinafter for the purpose of exemplification, is when the robot is coupled to a lawn mower. Such robot permits to mow the lawn in the absence of the owner, and at any suitable time, or to vacuum clean any predetermined premises.
Of course, safety means should preferably be provided to ensure safe operation of the robot. for instance, automatic shut-off of the robot should be provided, coupled to logic circuitry, to ensure that the operation of the robot is discontinued if one of a number of contemplated possibilities takes place. for instance, if the measured distance traveled without encountering a boundary exceeds by a threshold value the maximal linear distance within the bounded area, as calculated from the map of the boundaries, this may mean that the robot has exited the boundaries due, for instance, to a malfunctioning of the system due to which the proximity sensor has failed to identify the boundary. Other required safety means will be easily recognized by the skilled person, according to the type of robot and the intended use thereof.
The invention is further directed to an automated robot for operation within an enclosed area, comprising:
a proximity sensor positioned on the robot;
processing means connected to the said proximity sensor and receiving an input therefrom;
location means, to determine the coordinates of the robot relative to an arbitrary origin, at any specific time;
direction finding means; and
memory means to store values generated by the said processing means and, optionally, by the said location means.
The term xe2x80x9cproximity sensorxe2x80x9d, as used herein, indicates any device which is capable of detecting that the boundary of the working area is near. This may include, e.g., magnetic field detectors, acoustic signal detectors, bar code readers, resonance tag meters, transceivers, etc.
The invention also encompasses a system for automatically operating a robot within an enclosed area, comprising:
boundary means suitable for positioning along the perimeter of the working area, and of each area enclosed in the working area, in which it is desired the robot not to operate, the said boundary means being detectable by a proximity sensor;
a robot provided with a proximity sensor;
processing means on said robot, connected to the said proximity sensor and receiving an input therefrom;
distance-measuring means on the said robot, to measure the distance of the robot from a given starting point, at any specific time;
direction finding means;
memory means to store values generated by the said processing means and, optionally, by the said distance measuring means and/or direction finding means; and
motion means, to cause the robot to move.
In accordance with a further embodiment of the invention, a method for automatically cutting a lawn is provided. The method includes the steps of:
providing a lawnmower with a robot and at least a plurality of lawn height sensors;
cutting a first swath of lawn in a first direction;
performing a maneuver, under control of the robot and in response to output of the lawn height sensors, in a second direction generally opposite of the first direction to bring said lawnmower to a location parallel to but overlapping the first swath by a predetermined percentage as indicated by the different output of the lawn height sensors;
cutting a second swath of lawn parallel to the first swath while continually monitoring the lawn height output of said lawn height sensors thereby to ensure that the percentage of overlap is generally maintained;
repeating the steps of performing a maneuver and cutting a second swath for further swaths of lawn, wherein the previously cut lawn is denoted by said first swath of lawn and the swath to be cut is denoted by the second swath of lawn.
The maneuver can be an S-shaped maneuver and the grass height sensor can include the following elements:
a housing;
a rotatable wing against which grass can push, the wing having a pin attached thereto;
a fixed second pin, connected to the housing;
a spring attached around said pin, wherein the ends of the spring press against opposite sides of the wing and opposite sides of the fixed pin; and
means for measuring the angle of rotation of the rotatable wing.